GaAs radiation imaging detectors with an active layer thickness up to 1mm

Performance of a Medipix3RX Spectroscopic Pixel Detector With a High Resistivity Gallium Arsenide Sensor

“…Especially the very high achievable SNRs could allow shorter acquisition times without a substantial loss in image quality which, in turn, would lead to possible dose reductions for the patient, in addition to making the examination more bearable. Further, since this material does not exhibit instabilities in the electric field distribution or dead layers [21], its use in commercial mammography scanners appears promising. Measurements of mammographic phantom samples with Hexa modules are planned for the near future.…”

“…This technique previously demonstrated to provide sensors with resistivities in the order of cm [23], [28], [29] via high compensation rates. Due to the high dopant concentration, the width of the space charge regions (SCR) behind the metal (Schottky) contacts are small, leading to the bias voltage dropping mainly across the sensor and thus to a uniform distribution of the electric field [21], [24], [30]. This implies that the whole sensor volume is sensitive to radiation, and dead layers, which were sometimes reported to be present in epitaxial [31] and low-resistivity (EL2-compensated) bulk material with Schottky contacts [20], are absent.…”

“…In fact, GaAs in combination with photon counting readout chips has been considered promising for mammography since more than a decade [16], [17], and digital mammography prototype systems based on this material have already been developed [18], [19]. However, to our knowledge these systems were never applied widely, also due to substantial problems caused by the sensor material: GaAs sensors presented in the past were mainly based on rectified semi-insulating bulk material, which, despite showing good charge carrier transport properties and homogeneity, is limited in the thickness of the active layer [20] and can exhibit instabilities in the electric field distribution [21], preventing the routine use of these sensors in commercial systems.…”

“…It is based on the compensation of GaAs wafers by chromium (Cr) diffusion and has shown to provide fully active, high resistivity (HR) sensors with thicknesses up to 1 mm [21]. As was demonstrated recently [23], [24], these HR-GaAs:Cr sensors exhibit detector-grade material properties and, in combination with photon counting Timepix readout chips, provide an excellent image quality.…”

GaAs radiation imaging detectors for nondestructive testing, medical, and biological applications

“…Analysis of the state-of-the art digital radiographic systems shows that the greatest body of information is obtained from imaging systems based on semiconductor X-ray detectors (Si, GaAs, Cd 1-x Zn x Te). In Russia there are GaAs ionizing radiation detector technologies that enable detectors with an active layer thickness as great as 800µm to be developed, using wafers 76mm in diameter [1][2][3] . GaAs detectors have considerable promise due to their high radiation resistance and direct conversion of the X-ray quantum energy to electric signals.…”